1. Field of the Invention
This invention relates to motor controllers. More specifically, the invention is a motor controller system that provides a large dynamic range of motor operation for a single motor.
2. Description of the Related Art
Many mechanical drive system applications (e.g., robotics, materials processing furnaces, medical scanning devices, telescope drives, solar array drives, etc.) require that motor rates (e.g., revolutions per minute) be controlled for both very slow rates of much less than one revolution per minute and very high rates of several thousand revolutions per minute. In order to meet these requirements, the prior art has generally utilized two motors with associated control electronics for each motor. Typically, a stepper motor driven through a speed reduction gear is used to satisfy slow motor rate requirements while a DC servo motor is used to satisfy high motor rate requirements. Unfortunately, there are numerous problems with these two-motor systems. For example, stepper motors inherently waste power, are not normally designed to operate at high speeds, and have resonant frequencies of operation that can induce vibrations in the system to which the stepper motor is coupled. Further, use of reduction gears adds complexity and disturbances to the overall mechanical drive system. Still further, two-motor mechanical drive systems must utilize a clutching mechanism to clutch the stepper motor out of the system when high motor rates are required. Finally, the two-motors and associated electronics, clutching mechanism/gears add weight, size and cost to the overall mechanical drive system.